When organic molecules are used in a memory cell, the size of the memory cell can be reduced since the size of the organic molecule itself is small. Therefore, memory density can be improved. For this reason, an attempt is made to make a memory cell in which upper and lower electrodes are configured to sandwich molecules having function of changing resistance in response to presence/absence of electric field or injection of charge. In this memory cell, the resistance is changed using a voltage applied between the upper and lower electrodes, and the difference of a flowing electric current is detected.